Thread: if satement doesn't gaurd and yes i definatly have ==

i have written the following code that is probably full of bugs as i haven't had a chance to test it yet because at compile i get the following warning.

||=== Build: Debug in project 5 (compiler: GNU GCC Compiler) ===|
/home/ben/Documents/project euler/project 5/main.c||In function ‘divide’:|
/home/ben/Documents/project euler/project 5/main.c|42|warning: this ‘if’ clause does not guard... [-Wmisleading-indentation]|
/home/ben/Documents/project euler/project 5/main.c|43|note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘if’|
||=== Build finished: 0 error(s), 1 warning(s) (0 minute(s), 0 second(s)) ===|

here is the code

Code:

#include <stdio.h>
#include <stdlib.h>

#define MILLION 1000000

int divide(int num, int divisor);

int main()
{
    int result, num_divide, max_divisor;

    printf("Please enter the max number to divide by: ");
    scanf(" %d", &max_divisor);

    for (num_divide = max_divisor; num_divide < MILLION; num_divide++)
    {
        if((result = divide(num_divide, max_divisor)))
        {
            break;
        }
    }

    if (result == -1)
    {
        printf("naughty naughty you entered zero you cant divide by zero!\n");
    }
    else if (result == 1)
    {
        printf("there is no number between 1 and %d that can be divided by all the integers 1 to %d\n", MILLION, max_divisor);
    }
    else
    {
        printf("the smallest number that can be divided by all the integers 1 to %d is %d\n", max_divisor, num_divide);
    }
    return 0;
}

int divide(int num, int divisor)
{
    // sanity checks

    if (num == 0); //warning here
    {
        return - 1;
    }

    if (num % divisor != 0)
    {
        return 0;
    }
    if (divisor == 1)
    {
        return 1;
    }
    divide(num, divisor - 1);
}

coop

oops is the polite version of what just went through my mind lol

i am trying to find the smallest number that is devisable between 1 and n where n is entered by the user project euler asks for n to be 20 im up to 100,000,000 and still cant find a number that is devisable by 1 to 19 let alone a number that is devisable by 1 to 20.

to count between 20 and 100,000 as i have the for loop set up now takes a fair while when checking if each number is devisable by n (i know it breaks out of the divide function if a number isn't devisable by the current n but even so)
coop

The brute force method may require you to search all the way up to 20! (20 factorial), which is 2,432,902,008,176,640,000.

However, you should be able to simplify the problem by figuring out which factors are actually needed and then multiply them all together. For example, if the user enters 10, then (unless I'm mistaken) you need only the numbers 4, 7, 9, and 10, because if a number is divisible by those four numbers, then it's divisible by all integers between 1 and 10. So multiply 4*7*9*10 = 2520. Now the problem is figuring out which handful of numbers between 1 and n are required.

and 19 but my code takes longer to work out n = 19 than n = 22 even though its the same answer

that was the second thing that went through my mind the third isn't repeatable in public either